Publication No.32



E. Patiņo, A. Stashans. Structural and electronic effects 
in BaTiO3 due to Nb and La doping - XXXV Annual Conf. 
Finnish Phys. Soc., Juvaskyla (Finlandia), 2001, p.18.

Abstract:
	The reason of numerous investigations in BaTiO3 
crystal is its remarkable properties. Despite to the fact that 
many studies have been done so far on this ferroelectric material 
our knowledge of its fundamental properties are not satisfactory. 
Most of the studies carried out up to now are experimental. There 
are only few theoretical investigations (see [1] and Refs. 
therein) made up to date.
	Some effects in BaTiO3 due to the Nb and La-doping have 
been studied by means of the advanced quantum-chemical method INDO 
modified for crystal calculations based on the Hartree-Fock theory 
[2]. A LUC (Larger Unit Cell) consisting of 135 atoms has been used.
First, the effects under Nb impurity influence, in cubic phase of 
the material have been investigated. After the minimization of the 
total energy of the crystal. The obtained relaxation energy was 
found to be equal to 1.69 eV. An extra electron due to the Nb 
presence was found in the conduction band. In the tetragonal phase 
the relaxation energy is equal to 5.44 eV and an extra electron 
also jumps to the conduction band changing the state of the crystal.
When doping BaTiO3 with La the obtained relaxation energy was found 
to be equal to 0.94 eV. The extra electron due to the La atom was 
found to be situated in a local energy level within the band-gap.
In tetragonal phase the relaxation energy was obtained to be equal 
to 0.52 eV and again the extra electron is confined in the local 
energy level within the band gap. 

[1] H. Pinto, A. Stashans, Comput. Mater. Sci. 17 (2000) 73.
[2] E. V. Stefanovich, E. K. Shidlovskaya, A. L. Shluger, M. A. 
    Zakharov, Phys. Status  Solidi B 160 (1990) 529.  





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